1. Field of the Invention
The present invention relates to a switching mechanism of an air circuit breaker, a type of a low voltage circuit breaker, and more particularly, to a switching mechanism of an air circuit breaker that allows the overall size of the air circuit breaker to be compact by making the width of the switching mechanism relatively small.
2. Description of the Related Art
The air circuit breaker includes a switching mechanism that opens or closes a current conduction circuit, a cradle unit for housing the switching mechanism and having a terminal part connected with an external power source and a load, and a circuit monitoring and controlling unit that senses a fault current of the current conduction circuit as connected and provides a driving power for automatically driving the switching mechanism to a breaking (trip) position.
The present invention relates to the switching mechanism, which is called as a main circuit part of the major parts of the air circuit breaker, and the related art will now be described.
The switching mechanism of the air circuit breaker according to the related art will be described with reference to FIGS. 1 to 5 and 8.
First, the construction of the switching mechanism of the air circuit breaker according to the related art will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, the switching mechanism of the air circuit breaker according to the related art includes a stationary contactor 12 and a movable contactor 11 which is movable to a closing position at which the movable contactor 11 contacts with the stationary contactor 12 to close the circuit and a breaking (trip) position at which the movable contactor 11 is separated from the stationary contactor 12 to open the circuit.
As shown in FIG. 1, the movable contactor 11 is connected with a main shaft lever 10-1 and driven such that it comes in contact with the stationary contactor 12 or separated from the stationary contactor 12 according to a rotational direction of the main shaft lever 10-1.
The main shaft lever 10-1 is generally used when the air circuit breaker opens and closes 3 phases alternating current conducting lines, so three main shaft levers 10-1 are provided to correspond to each phase and drive the movable contactor 11 of a corresponding phase.
In order to simultaneously drive the three main shaft levers 10-1, the respective main shaft levers 10-1 are coaxially connected with a single common main shaft 10.
Accordingly, the main shaft 10 penetrates both side plates 1 supporting the switching mechanism so as to extend to be connected with the main shaft lever 10-1 of a different phase.
Among the main shaft levers 10-1, the central main shaft lever 10-1 connected with the switching mechanism has one end connected with the main shaft 10 and the other end connected with a first link 6.
Like gears which have a different rotational shaft and are in mesh with each other, one end of the first link 6 is connected with the main shaft lever 10-1, and the main shaft lever 10-1 and the first link 6 are rotated in the mutually opposite directions. The first link 6 provides a driving force to the central main shaft lever 10-1, among the three main shaft levers 10-1, to allow the central main shaft lever 10-1 to drive the movable contactor 11 to an opening or closing position.
A second link 4 is connected with the other end of the first link 6, and the first and second links 6 and 4 are rotated in the same direction.
One end of a third link 3 is rotatably provided at the other end of the second link 4 and connected by a driving connection pin (P) to transfer the driving force to the second link 4.
A closing spring unit includes a closing spring 13 for providing a driving force to drive the movable contactor 11 to the closing position and a closing spring seat (no reference numeral is given). The closing spring 13 charges elastic energy and discharges it to provide a driving force to allow the movable contactor 11 to be driven to the closing position.
In order to prevent the closing spring 13 from being released and support the rotation of the closing spring seat, a closing spring support bracket 15 is provided to support the other end of the opposite side of the end portion that provides the driving force.
The switching mechanism of the air circuit breaker according to the related art comprises a charging cam 2 for providing a driving force for charging elastic force of the closing spring unit, and the charging cam 2 is rotatable together with the rotational shaft 2a. The charging cam 2 includes a cam roller 2b indicated as a dotted line on one side thereof as shown in FIG. 2.
The third link 3 is coaxially connected with the rotational shaft 2a of the charging cam 2 and rotatable together.
A pair of driving levers 16 include a driving lever pin 16b that contacts with the second link 4. The pair of driving levers 16 are separately connected by the driving lever pin 16b, and the second and third links 4 and 3 are interposed between the pair of levers 16. The driving levers 16 can be connected with the closing spring unit to provide a driving force for charging elastic energy to the closing spring unit, or can be rotatable upon receiving charged elastic energy from the closing spring unit.
A breaking spring 14 is provided such that one end thereof is supported by the main shaft lever 10-a and the other end is supported by a spring support pin (reference numeral is not given) fixed on the side plate 1. During a closing operation, the breaking spring 14 is stretched according to clockwise direction of the main shaft lever 10-1 to charge elastic energy, and when a circuit is broken, the breaking spring 14 discharges the charged elastic energy to provide a driving force for rotating the main shaft lever 10-1 counterclockwise.
A pair of third link bias springs 15 are provided. One end of each third link bias spring 15 is supported by the driving lever pin 16b of the driving levers 16 and the other end of each third link bias spring 15 is supported by the driving connection pin (P) that connects the second and third links 4 and 3.
The driving connection pin (P) penetrates the second and third links to connect them, and extends to be protruded to support the pair of third link bias springs 15 at both ends.
In order to prevent interference by the protruded driving connection pin (P), the pair of driving levers 16 are separated by the driving lever pin 16b with a considerably long distance therebetween.
A closing latch 5 extends long in a vertical direction in order to have one surface positioned on a moving locus of the cam roller 2b provided on one surface of the charging cam 2, and can latch a rotation of the charging cam 2. An upper end portion of the closing latch 5 is positioned on a rotating path of an on-shaft 8, so it can be latched or released by the on-shaft 8.
The on-shaft 8 is connected with an on-button (not shown) so as to be rotated manually or automatically rotated by being connected with an electrical driving control device or an actuator.
A recess 3a is formed at an upper portion of the third link 3, an opening latch roller 7a is provided at a position at which it can enter the recess 3a of the third link or released therefrom. An opening latch 7 that can be rotatable centering around a rotational shaft 7b is provided at an upper portion of the third link 3. One end of the opening latch 7 is connected with an opening latch spring 7c by a pin to thus receive an elastic bias force for rotation counterclockwise in FIGS. 1 and 2 from the opening latch spring 7c. 
An off-shaft 9 is provided to contact with the other end of the opening latch 7 in a lengthwise direction, and the rotation of the opening latch 7 is latched or released by the off-shaft 9.
The operation of the switching mechanism of the air circuit breaker according to the related art constructed as described can be divided into the elastic energy charging operation, the closing operation and the opening operation of the closing spring and will be described as follows.
First, the charging operation of the closing spring will be described with reference to FIG. 3.
The rotational shaft 2a of the charging cam 2 is rotated by an operating handle (not shown) or a driving motor (not shown) counterclockwise on the drawing.
Then, the driving lever roller 16a of the driving lever 16 contacting with an outer circumferential surface of the charging cam 2 is compressed as a curvature radius of the outer circumferential surface of the charging cam 2 is reduced to press the spring seat of the closing spring unit that contacts with and pressed by the driving lever roller 16a to compress the closing spring 13.
At this time, as the charging cam 2 is rotated, the driving lever roller 16a rolls along the outer circumferential surface of the charging cam 2, and the charging cam 2 is rotated until the cam roller 2b provided at one surface of the charging cam 2 contacts with the closing latch 5.
As the charging cam 2 is rotated counterclockwise, the third link 3, the second link 4 and the driving lever 16 interlock to be rotated counterclockwise.
At this time, rotation of the main shaft 10 is latched by the opening latch 7, so that it is maintained to be separated from the movable contactor 11 and the stationary contactor 12 as shown in FIG. 1.
As the third link 3 is rotated counterclockwise, the roller 7a of the opening latch 7 is received in the recess portion 3a of the third link 3 and the counterclockwise rotation of the third link 3 is latched.
When the cam roller 2b provided on one surface of the charging cam 2 contacts with the closing latch 5, it pushes the closing latch 5, making the closing latch 5 be rotated in clockwise direction centering around its rotational shaft. The clockwise rotation of the closing latch 5 is restraining by the on-shaft 8, and the charging operation of the closing spring 13 is completed.
The closing operation of the switching mechanism of the air circuit breaker according to the related art will now be described with reference to FIG. 4.
When the on-shaft 8 is connected with an ON-button (not shown) and rotated manually or when the on-shaft 8 is connected with the electrical driving control device or the actuator and automatically rotated, the closing latch 5 is released from the on-shaft 8 and rotated clockwise.
As the closing latch 5 is released, the cam roller 2b is also released from the closing latch 5.
Accordingly, the driving lever roller 16a which has restraining discharging of elastic energy of the closing spring 13 while contacting with the outer circumferential surface of the charging cam 2 gets out of the outer circumferential surface of the charging cam 2.
As the closing spring 13 is discharged, the driving lever 16 is pressed by the spring seat of the closing spring 13 and rotated counterclockwise, and accordingly, the driving lever pin 16b pushes the second link 4 to rotate it counterclockwise. Then, the third link 3 is rotated counterclockwise according to the counterclockwise rotation of the second link 4, and accordingly, the first link 6 is pushed up by the second link 4 and rotated counterclockwise.
The main shaft lever 10-1 and the first link 6 are connected with each other for interlocking, so that as the first link 6 is rotated counterclockwise, the main shaft lever 10-1 is rotated clockwise and the main shaft 10 is also rotated clockwise. Accordingly, the movable contactor 11 interlocked with the main shaft lever 10-1 is rotated counterclockwise on the drawing and comes in contact with the stationary contactor 12 and thus the circuit is closed.
At this time, the breaking spring 14 is in a stretched state, storing (charging) the elastic energy.
The circuit opening operation of the switching mechanism of the air circuit breaker according to the related art will now be described with reference to FIG. 1.
When the off-shaft 9 is connected with the OFF-button (not shown) and rotated clockwise manually or when the off-shaft 9 is connected with the electrical driving control device and the actuator and rotated clockwise automatically, the opening latch 7 is released from the latched state by the off-shaft 9 and rotated counterclockwise due to elastic force of the opening latch spring 7c, and also released from the latched state by the recess portion 3a of the third link 3.
As the third link 3 is released from the latched state by the opening latch 7, the interlocked second and first links 4 and 6 are also released, and in a state that the opening spring 14 is stretched while closing operation, a support end portion of the main shaft lever 10-1 is returned to the spring support pin of the side plate 1 to discharge the charged elastic energy to thus rotate the main shaft lever 10-1 counterclockwise. Accordingly, the movable contactor 11 is rotated clockwise and separated from the stationary contactor 12. Thus, the circuit is opened.
However, in the switching mechanism of the air circuit breaker according to the related art, as shown in FIG. 8, one end of each of the pair of third link bias springs 15 is supported by the driving lever pin 16b of the driving lever 16 and the other end of each of the pair of third link bias springs 15 is supported by the driving connection pin (P) that connects the second and third links 4 and 3.
The driving connection pin (P) penetrates the second and third links to connect them, and extends to be protruded to support the pair of third link bias springs 15 at both ends.
In order to prevent interference by the protruded driving connection pin (P), the pair of driving levers 16 are separated by the driving lever pin 16b with a considerably long distance therebetween.
Thus, because the space between the pair of driving levers 16 becomes away, the distance between the both side plates 1 is increased, the width of the switching mechanism of the air circuit breaker is increased, and the air circuit breaker is increased in size.